Don't strip trailing newlines but keep them in the diff.

This *should* work as we transform to a normalised form before diffing.
However, I think the reason for the change ultimately was Windows, where
crlf/lf differences might make diffs light up unnecessarily.

Maybe there will be more polish in that regard.
Unfortunately it's also not clear anymore why stripping was deemed so very
necessary in the first place.

Author: Byron

crates/but-core/src/unified_diff.rs

@@ -187,7 +187,10 @@ impl UnifiedDiff {
                         Ok(())
                     }
                 }
-                let input = prep.interned_input();
+                let input = gix::diff::blob::intern::InternedInput::new(
+                    prep.old.intern_source(),
+                    prep.new.intern_source(),
+                );
                 let uni_diff = gix::diff::blob::UnifiedDiff::new(
                     &input,
                     ConsumeBinaryHunk::new(ProduceDiffHunk::default(), "\n"),